dsh-chat-offscreen
Keep long DeepSeek Harness (DSH) Web chat sessions responsive.
The problem
The DSH chat transcript is not virtualized upstream: every loaded history
page stays in the DOM. Backwards paging pulls 50 messages per loadOlder()
page, and the turn rail's jump loader pulls 200-message pages until the window
covers the target — with no eviction. On a long session, dragging the
transcript width handle, the sidebar divider, or simply scrolling forces
layout + paint across thousands of nodes, which makes the UI stutter.
What this plugin does
It is a tiny client-side plugin that installs one stylesheet:
[data-chat-flow-kind="assistant-step"]:not(:has(.md-table-wide)),
[data-chat-flow-kind="tool-call"]:not(:has(.md-table-wide)) {
content-visibility: auto;
contain-intrinsic-size: auto 120px;
}
[data-chat-flow-kind="assistant-step"]:has(.md-table-wide),
[data-chat-flow-kind="tool-call"]:has(.md-table-wide) {
content-visibility: visible !important;
contain: none !important;
}
content-visibility: auto lets the browser skip layout and paint for
off-screen assistant steps and tool calls — a cheap approximation of
virtualization — while contain-intrinsic-size: auto 120px keeps the scroll
range stable and remembers a row's measured height once seen. Rows containing a
wide markdown table opt out so their breakout width is never mis-estimated.
This is a rendering-layer workaround, not a data change: no messages, session
events, or host state are touched. It composes with the retired
@linxin666/dsh-perf P0 rule of the same shape.
Install
dsh plugin --profile web add github:publieople/dsh-chat-offscreen
Then restart the web profile (dsh web ...) and hard-refresh the page
(Ctrl+Shift+R). The lib/ build is committed, so no package build script
runs and no allowBuilds entry is required.
The bundle patch inserts the plugin row automatically. If you install by hand:
cd "$DSH_HOME/profiles/web"
pnpm add github:publieople/dsh-chat-offscreen
then add dsh-chat-offscreen to dsh.profile.bundles in that profile's
package.json and restart.
Verify
Open a long session and drag the transcript width handle / sidebar divider, or
scroll fast. In DevTools → Elements, an off-screen assistant step should carry
content-visibility: auto.
Disable / uninstall
dsh plugin --profile web remove dsh-chat-offscreen
then restart. Removing the plugin removes the stylesheet; nothing is persisted.
Compatibility
- Client platform:
web. Host half is intentionally empty.
- Depends only on the browser
content-visibility feature (Chrome/Edge 85+,
Firefox 125+, Safari 18+). On older engines the rules are inert and the UI
simply stays as before.
- Built against DSH
0.1.5-rc.1; the plugin uses no DSH runtime imports.
Development
npm install
npm run typecheck
npm run build # tsdown -> lib/index.js (ESM) + lib/client.js (ModuleLoader)
npm test # drives the built client bundle against a fake DOM
lib/ is committed on purpose so Git installs need no build step. If you change
src/, re-run npm run build and commit the result.
If upstream virtualizes the chat
When the DSH chat surface gains real virtualization, delete this plugin row.
The upstream trajectory view (ui-trajectory) is already virtualized; the chat
surface is not.
